Engine synchronizer



Aug. 5, 1941. M, F, BATES 2,251,388

ENGINE SYNCHRONIZER Filed Aug. 3, 1938 3 Sheets-Sheet l w consum speso Toma TO OIL PUMP Aug. 5, 1941.

M. F. BATES ENGINE SYNCHRONIZER Filed Aug. 5, v1938 5 Sheets-Sheet 2 ENGlNE I* Aug. 5, 1941. M F, BATES 2,251,388

ENGINE SYNCHRONIZER Filed Aug. 3, 1938 3 Sheets-Sheet 5 llNVENT O MoYnr/MER BnTEs Patented Aug. 5, 1941 ENGINE SYNCHRONIZER Mortimer F. Bates, Brooklyn, N. Y., assigner to Sperry Gyroscope Company,

Inc., Brooklyn,

N. Y., a corporation of New York Application August 3, 1938, Serial No. 222,785

(Cl. Sli-97) 5 Claims.

This invention relates to new and improved means for equalizing or synchronizing the speeds of the several engines of a multi-engine aircraft. It has been proposed to control speeds of the engines by using one engine as the measure of the speed for the other engines. However, according to my invention, I prefer to use a master speed control to whichall engines are automatically synchronized. Y

This invention further provides novel means byl which the -speeds of the engines can be controlled either by automatically adjusted individual throttles or by automatically adjusting the pitch of the propeller blades separately for each engine, or both.

Another object of the invention is to provide a single master control handle by which the engine speeds can be set at will to any desired speed.

Referring to the drawings showing one form which my invention may assume:

Fig. 1 showsthe general arrangement of the synchronizing device.

Fig. 2 shows in detail the contacting arrangement of the control unit. l

Fig. 3 shows the arrangement of the engine throttle control.

Fig. 4 shows the general wiring diagram.

Fig. 5 is a detailed view of the reversing device used in the master speed control.

, Fig. 6 is a schematic diagram of the general arrangement of the controls for a 3 motor airplane.

Fig. '7 is `a vertical section of the preferred actual construction of the main portion of my synchronizing device.

Fig. 8 is a detail showing the locking detent.

In Fig. 1, I, 2 and 3 are the engines of a multiengine airplane, having propellers 4 oi' the ad justable pitch type, and preferably of the electric motor-driven adjustable-pitch type, in which the motor and the gearing are contained in the housnig 5, while slip rings 6, 1, and 8, together with brushes 9, I and II, serve the purpose of conducting the electric current to the motor for control of the pitch of the propeller. Self-synchronous transmitters I2, I3 and I4, driven from the engine shaft, are connected to repeaters of the same type of which only repeater I is shown in Fig. 1. This repeater is shown as connected by cable I8 to its transmitter I2 and by cable I1 to l the A. C. current supply.

As is well known, the repeater will rotate in synchronism with its transmitter if the transmitter is rotated by the engine and therefore shaft I8 will rotate pinion I9 at engine speed.

, rotated by gear This pinion, in turn. rotates one arm 20 of a dinerential 2l, the second arm 22 of which is 23. The third arm of the differential carries gear or toothed disc 24 and also turns shaft 25. Slidingly mounted on shaft 25 is a hub 26 mounting on an insulated portion 26', an arm 21 (Fig. 2) bearing two contacts 28 and 29. Hub 26 is held to shaft 25 by a slight amount of friction which may be furnished by a double conical shaped resilient member 2l' housed in the hub 28 and subjected to pressure by a closure plug 25. Hub 26 and arm 2-1 are located on the inside of a drum 30, carrying on the outside two insulated slip rings 3I and 32. Also mounted on the drum, but on the inside, are two insulated contacts 33 and 34 which are electrically connected to slip rings 3| and 32, respectively, and which are adapted to be engaged by contacts 28 and-29 of the movable arm 21. The contact spring 35 serves to carry current to the contacts 28 and 29 and two brushes 36 and 31 carry current to the contacts 33 and 34, through the slip rings 3| and 32.

Gear 23 is mounted on shaft 38 which also carries a bevel gear 39 meshing with bevel gear 40 which is mounted on the shaft of the roller 4I of a variable speed drive mechanism. A constant speed motor 42 drives the disc 43 of this mechanism at a constant speed so that the roller 4I is driven at a speed proportional to the position of the ball-carriage the disc 43.' The position of the carriage 44 may be varied by means of the master speed control lever 45, so that roller 4I rotates with a speed determined by the position of the handle 45.

The other end of the roller 4I is connected to an electric tachometer 46 which in turn energizes the indicator 41 on which the true speed of the roller 4I can be read. The dial of the indicator also may be calibrated to read the'speed of the airplane engines.

The operation of the device is as follows: By adjusting lever 45, the roller 4I is rotated at a speed proportional to that at which it is desired to synchronize the engines of the ship. The roller 4I through its associated gearing and shafting rotates pinion 23 and meshing gear 22. Gear 20 is rotated in the opposite direction by the engine I through repeater motors or selsyns I2 and I5. If the speed of the gears 2II and 22 are equal, shaft 25 will standstill and contact arm 21 will not move. If the engine changes speed. gear 20 runs slower or faster, as the case may be, and the diiierence of its speed as compared to that of gear 22 Will appear as a rotation,

44 with respect to the center of either clockwise or counter-clockwise of shaft 25 and arm 21.

After a predetermined time lag, if the resulting rotation is assumed to be clockwise, as viewed in Fig. 2, contact 28 will engage contact 33 and thereby establish a circuit energizing a relay 48. j

This relay in turn will either slowly change the propeller pitch or the position of the throttle lever of the engine, thereby slowly changing the engine speed until shaft 25 stands still again. It also simultaneously energizes one of the magnets, for example, magnet 49, of a reversing device having oppositely acting magnets 49 and 49'.

The drive shaft 50 of this device is rotated at a constant speed by the motor 42 through gears 5I and 52 and carries two friction cones 53 and 54. A third and larger friction cone is carried on a shaft 56 which has its bearings in the movable arm 56.

As is shown in Figs. 5 and 7, this arm 56' carries at its outer end an armature 51 and is universally pivoted at its other end on xed pin |58. The shaft 56 carrying the friction disc 55 is journalled in said arm and is connected through universal joint 51' to a shaft 58 journalled in fixed bearings 58 and 59 (Fig. 1), in such a way as to prevent axial movement. Universal joint 51 acts as a second pivotal support for the arm 56. Shaft 58 is shown as carrying a worm 60 meshing with gear 6I mounted on a sleeve 62 which is secured to and carries the drum 30.

If, now, the coil of magnet 49 is energized, armature 51.will be pulled towards the core of this magnet and will swing the shaft 56 in a conical arc around ball joint |58 and the center point of the universal joint 51'. The cone disc 55 partakes of this motion and cornes into contact with conical roller 54, which rotates it in such a direction as to cause worm 6l) to turn drum 30 in a clockwise direction as viewed in Fig. 2, thereby interrupting the circuit between contacts 28 and 33 at the time the rotation of contact arm 21 falls behind the rotation of drum 30. Thereupon, the relay 48 is interrupted and leaves the propeller pitch motor or the throttle in the last adjusted position. At the same time, magnet 49 is de-energized and conical disc 55 returns to its neutral position under the inuence of leaf springs IIII and IIII so that further rotation of the drum is stopped. These springs are mounted on a block III, below arm 56 by means of screws II2 and II2.

It will be apparent that with drum 30 driven at a constant speed from motor 42, the connection between contacts 33 and 28 is broken while arm 21 is still rotating at a speed only slightly less than that of the drum. Since rotation of the arm 21 indicates a lack of synchronism between the engine and the master speed device, it is evident that the connection between contacts 33 and 28 is broken before the correction of the engine speed has been completed, that is, before synchronism is reached. This is a desirable condition since it tends to prevent the speed adjusting mechanism overshooting the position of synchronous speed and hunting about that position. After the disengagementof contacts 33, 28, due to the arm 21 falling behind the rotation of drum 30, if momentum of the moving parts has not carried the adjusting mechanism to the position of synchronism and if the disagreement of the engine and master speed device is still in the same sense, arm 21 will slowly travel around -a differential movement, each division it passes indicates a gain or loss of one revolution with respect to the master speed setup. I purposely space contacts 33 and 34, 320 degrees or more apart, thus permitting about eighteen revolutions to accumulate before a correction of synchronization takes place. For example, if arm 21 passes over ve divisions in l/3 of one minute, the lack of synchronism at the time amounts to ve divided by 1/3, or 15 R. P. M. The above construction allows the synchronizer to pass over momentary speed differences which otherwise would cause unnecessary activity of the corrective means at the propeller or throttle.

As is well known, selsyns cannot be accelerated suddenly without falling out of step. If therefore, the engines of the airplane are running at high speed at the time the automatic synchronizer is energized, the repeater I5 cannot follow the fast running transmitter |2, but will just oscillate without revolving. I provide a very simple and novel means to bring the repeater up to speed by providing a pawl |20, Fig, 1, which can be depressed to engage the teeth of gear 24 by means of push-button I2I. If this button is depressed, the gear 24 cannot rotate, and the gear 20 will rotate with the same speed as, but in the opposite direction to gear 22, which is driven from the master variable speed drive mechanism by motor 42. Gear 20 will drive gear I9 and thereby repeater I5 at a speed, adjustable by lever 45 to engine speed, at which time the pushbutton may be released. Repeater I5 will now continue to run i'n synchronism with transmitter I2.

Fig. 3 shows the hydraulic cylinder connected to the engine throttle lever |11, the control valve 62 of which is controlled by a push-pull electro-magnet 63. Valve and cylinder may be of any conventional design, as in use on planes today, for example, in the hydropneumatic automatic pilot disclosed in U. S. Patent No. 1,992,970, issued March 5, 1935, of which the present applicant was one of the joint inventors. When the valve B2 is displaced slightly in one direction or the other from its normally centralized position, oil is admitted slowly to one end of the cylinder 11 to slowly readjust the throttle lever |11.l

The control of this electromagnet is vested in relay 48. A manual throw-over switch 16, Fig. 4, allows the pilot or operator to select at will whether the motor speed adjustment is to be performed by the propeller pitch motor or by the engine throttle.

The electric connections by means of which the various controls are interconnected are shown in the wiring diagram, Fig. 4, in detail, the lead wires 82, 83, 84, B5, and 95, being similarly marked in Figs. 1 and 4. n

A source of electric energy, shown as'a ,bat tery 64, supplies the electric circuits.4 'lIhj connections to only one or the engine speedlcontrol mechanisms are shown, the lother two being indicated by arrows which would lead to similar points of the other two circuits to lbe connected in parallel.

A switch 65 has two positions by which the control of the speed `correcting apparatus can be transferred from the contacts`29 and 29 to pushbuttons 69 and 10. If the switch 65 is in aposition where the switch blades make contact with the points 66 and 61, thecontacts 28 and 29 control the operation; The two signal lights 91 and 90 are so connected in the circuit that the light 91 glows whenever contact 33 tact 28, while light 99 glows when contact 29 engages contact 34. These lights, therefore, indicate directly whether or not the speed of the engine is increasing or decreasing, and as long as they are extinguished, the pilot knows that the engines are synchronized; If the switch 65 is in the position shown, where its blades make contact with the points 90 and 8|, the manually operated push-buttons 69 and 10 take over control of the synchronizing apparatus. The lights operate as before bythe contact arm, so that the glowing of a light is a signal to press the corcorresponding push-button until the light is extinguished. The relays 48 each have two coils 12 and 12' adapted to operate two single-pole, single-throw switches 14 and-15. These switches, in turn, control the sense in which speed corrections are applied, while the switch 16 controls the selection of the particular type of speed control apparatus to be used. If switch 16 is moved clockwise to make contact with points 92, 93 and 94, the synchronizer actuates the push-pull magnet 63, having two coils 95 and96 and controlling the position of the hydraulic throttle 11. If switch 16 isA turned counterclockwise and makes contact with points 81, 86 and 89, the propeller pitch motor is connected into thecontrol circuit.

the engine synchronizer may be arranged on an airplane. The masterA speed control 99 and the three individual engine speed controls are mounted in a common casing |00, on the outside of which appear the main speed adjusting lever 45, the transfer switch 65, the signal lights 91 and 98 and the push-buttons 69 and 10. The three individual relays 49 are contained in the boxes R and are shown as connected to a switch box containing the multiple switch 16 which is shown in a position to effect speed control by means of the propeller pitch motor. The individual engine throttles |02. |03 and |04 are also connected to the switch box |0|. It is clearly evident from Fig. 6 that the arrangement of the apparatus allows 'quick and eicient control of all three engines, whether manually by operating the three individual throttles if the whole system is disconnected. or manually by means of the push-buttons 69 and 10, or fully automatic, by adjusting the main speed control lever 45 and' by selecting through switch 16 either the propeller pitch motor or the hydraulic engine throttle as thecontrolling agent.

From the foregoing, the operation of my invention will bevreadily understood and its aflvantages over previous systems appreciated. By employing a master speed controller for all engines, Iravoid a serious defect in prior art devices in which the speed of one engine is compared with the'speed of another engine since in my invention the failure of one engine does not affect the others, Whereas, in the prior art. if the master engine fails the automatic regulating device would shut down all engines. Also by my invention, I avoid the serious and uncomfortable hunting action that takes place in most of the prior art devices in which the control Fig. 6 shows how the various components of causes continuous accelerations and decelerating about the desired synchronous speed. This is avoided in my invention by my special means for breaking the contacts 29, 29 and 33, 34, shortly prior to the reaching of synchronous speed y whereby synchronism is approached in slow steps is engaged by conrather than overrun with resulting hunting. With my invention, the same air speed will be maintained because all engines are automatically forced to run at substantially synchronous speeds. Also the troublesome beat vibrations caused by unequal engines are fully eliminated.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made Without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim and desired to secure by Letters Patent is:

1. An engine synchronizer comprising, means for obtaining a desired constant master speed, a differential gear` train, means to drive one arm of said differential from the engine, means to drive another arm of said differential from said first named means, contact means frictionally mounted for rotation by the third arm of said differential, complementarycontact means mounted for rotation with respect to said other contact means, means to reversibly rotate said complementary contact means at a predetermined rate of speed in the same direction as said rst contact means, a relay operated by said contact means, reversible friction driving means for rotating said complementary contacts, electromagnetic means actuated by said relay to control the direction of rotation of said driving means, and means simultaneously operated by said relay to effect changing of the engine speed.

2. In an apparatus for synchronizing the engines of a multiple-engine craft to within a given Alimit of speed difference with respect to a se- `justing engine speed to said standard speed, comprising means responsive to said speed difference, relay means energized by said speed responsive means to cause gradual speed variation of each engine and power means also controlled by said relay for deenergizing said relay when said speed difference is Within a predetermined limit.

l3. An engine synchronizer, comprising, means for obtaining an adjustable constant master speed, a controller for adjusting said speed, a differential gear train, means for driving one arm of said differential gear train from the engine, means for driving another arm of said differential gear train from said constant speed means, contact means frictionally mounted for rotation by the third arm of said differential, complementary contact means mounted for rotation relative to said first contact means, a relay operated upon engagement of said two contact means, normally inoperative reversible Yfriction driving means for rotating said complementary contact means to cause disengagement from said rst contact means, electromagnetic means actuated by the operation of said relay for rendering said last means operative, a variable pitch propeller, and means controlled by said relay for changing the pitch of said propeller to cause said engine to change speed while said relay remains operated.

4. Ari engine synchronizer comprising, means for obtaining an adjustable constant master speed, a controller for adjusting said speed, a differential gear train, means for driving one arm of said differential gear train from the engine, means for driving another arm of said differential gear train from said contant speed means, contact means frictionally mounted for rotation by the third arm of said diiierential, complementary contact means mounted for rotation relative to said first contact means, a relay operated upon engagement of said two contact means, normally inoperative reversible friction driving means for rotating said complementary contact means to cause disengagement from said rst contact means, electromagnetic means actuated by the operation of said relay for rendering said last means operative, means for positioning the engine throttle and means actuated by said relay for controlling said positioning means to. effect a change of Y engine speed. Y

5. In an engine synchronizer for multiple-engine craft, a constant speed motor, an adjustable speed device driven thereby providing an adjustable common master speed for al1 engines, means individual to each engine for adjusting the speed thereof responsive to the difference between each engine speed and the master speed, each comprising a mechanical differential, means for driving one arm of said differential at master speed from said adjustable speed device, means for driving a second arm of said diierential at engine speed including an enginedriven transmitter and a repeater actuated thereby, and means actuated by rotation of the third arm of said differential for varying the engine speed of each connected engine, respectively.

MORTIMER F. BATES. 

